In the 3rd Generation Partnership Project (3GPP), a radio access method and a radio network for cellular mobile communication (hereinafter referred to as “Long Term Evolution (LTE)”, or “Evolved Universal Terrestrial Radio Access (EUTRA)”) have been studied. In LTE, a base station device is also referred to as an evolved NodeB (eNodeB) and a terminal device is also referred to as User Equipment (UE). LTE is a cellular communication system in which an area is divided in a cellular pattern into multiple cells, each being served by a base station device. A single base station device may manage multiple cells.
LTE supports Time Division Duplex (TDD). LTE that employs a TDD scheme is also referred to as TD-LTE or LTE TDD. In TDD, an uplink signal and a downlink signal are time-multiplexed.
In the 3GPP, application of a traffic adaptation technology and an interference reduction technology (DL-UL interference management and traffic adaptation) to TD-LTE has been studied. The traffic adaptation technology is a technology that changes a ratio between an uplink resource and a downlink resource according to uplink traffic and downlink traffic. The traffic adaptation technology is also referred to as a dynamic TDD.
NPL 1 discloses a method of using a flexible subframe as a method of realizing traffic adaptation. The base station device can perform reception of the uplink signal or transmission of the downlink signal on the flexible subframe. In NPL 1, as long as the base station device does not instruct the terminal device to transmit the uplink signal on the flexible subframe, the terminal device regards the flexible subframe as the downlink subframe.
NPL 1 discloses that Hybrid Automatic Repeat reQuest (HARQ) timing for a physical downlink shared channel (PDSCH) is determined based on an uplink-downlink (UL-DL) configuration that is newly introduced and that HARQ timing for a physical uplink shared channel (PUSCH) is determined based on an initial UL-DL configuration.
NPL 2 discloses (a) that an UL/DL reference configuration is introduced and (b) that several subframes can be scheduled by a dynamic grant/assignment from scheduling for either uplink or downlink.